Changes in the design of automobiles, particularly recent trends toward smaller more fuel efficient designs, have resulted in new body styles, and one significant feature which appears in the various models of different manufacturers is the so-called hatchback door for easy access to the rear interior of the smaller automobiles. Many of these hatchback doors utilize a device which is often referred to as a "gas spring" to urge the door into a raised open position. In reality, these are small cylinder-piston devices which extend in a linear direction under the force of gas which is trapped under pressure between the piston and the head of the cylinder. The head of the cylinder has a ball socket, usually integrally formed with the cylinder, which engages a ball on the body framework or on the door, and the end of the piston likewise has a similar socket, often integrally or at least non-removably formed to the outer end of the piston rod, and adapted to engage a further ball on the door or on the body framework. In practice, one of these devices is employed at each side of the hatchback door.
A noticeable problem has been recognized by owners of automobiles having these devices, due to the wear on the gas spring mechanism. The ball joints at its ends must transverse a rather large angle, and at time the forces on the parts, particularly on the sockets, are directed substantially away from the longitudinal center line of the devices. Since these devices are mass produced and often use molded plastic parts, there is a tendency for the plastic ball sockets to distort, enlarge, or tear, and eventually to release from the ball where the stress tends to be concentrated. Failure at either end, in the past, has required the automobile owner to buy an entire replacement assembly, due to the integral or non-removable nature of the ball sockets on the devices.
Not only are structurally sound parts wasted, but from the viewpoint of the consumer there is unneeded monetary expenditure to replace the entire gas spring assembly, when only the ball joint has failed. The present invention has been developed in response to this problem and need.